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Seahawks get lucky enough to face Chiefs in primetime

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Kansas City Chiefs v Seattle Seahawks Photo by Otto Greule Jr/Getty Images

On Sunday night the Seattle Seahawks will host the Kansas City Chiefs, potentially with a shot at securing a playoff berth on the line depending on how the games earlier Sunday go. The Chiefs bring their explosive offense to town, and look to take advantage of a young and beat up Seattle secondary. The Hawks, of course, will look to take advantage of the fact that they are playing at home, and perhaps one of the biggest things that will be in their favor will be the simple fact that the game is being played in primetime.

The Seahawks have been extremely, extremely good in primetime in recent seasons, with key primetime victories in recent years including the 2016 victory over the New England Patriots and the 2017 defeat of the Philadelphia Eagles. In fact, since Pete Carroll arrived in Seattle the Hawks have been among the best teams in the NFL in primetime.

What’s the secret to the Seahawks primetime success? We don’t really know the answer to that, however, last month I took a very high level look at whether or not the Hawks might be better suited to play in primetime simply because of the fact that they play on the West Coast.

Some fans didn’t like the proposed idea that the Hawks could be enjoying an advantage simply because of the fact that they play on the West Coast, demanding a more rigorous look into the effects of time zone differences when it comes to the games in question. As noted in the previous article, it was a very high level analysis that was only attempting to determine whether this was something that would be worth looking into in more depth.

Based on the results, I certainly thought so, so I dug deeper and here’s some of what I found.

Specifically, what I did was to look at every single primetime game that has been played in the NFL since 1976 when the Seahawks entered the league. From that sample of 1,449 primetime games, I eliminated games between teams from the same time zone or only one time zone apart. Thus, for an example for those older Hawks fans who remember the AFC West days, the sample eliminates any primetime games against the Oakland-then-Los-Angeles-but-now-back-in Oakland Raiders, the Los Angeles (nee San Diego) Chargers and the Denver Broncos. However, because of the two time zone difference between Seattle and Kansas City, it does include primetime games against the Chiefs, including the 1999 monsoon game at Arrowhead which saw weather delays due to thunderstorms.

In any case, the result was a sample of 332 games played in primetime between two teams that had a two or three hour time zone difference between their home cities. The results from the sample show that in these games, 55.42% of the time the team from further west won, and that takes nothing into consideration outside of the home location of the two teams.

As Josh Hermsmeyer (@friscojosh on Twitter) noted in an piece for FiveThirtyEight.com Friday, the home team wins over 57 percent of games played at the NFL level. Looking at the numbers for the same timeframe from which my primetime numbers are drawn, since 1976 NFL teams playing at home enjoy a .5781 winning percentage (5,834-4,255-23 per Pro-Football-Reference.com).

Thus, when a team from the Mountain or Pacific Time Zone (or, technically also from the Arizona Time Zone since Arizona splits the season between these two time zones. For the purposes of this analysis, games in which the Arizona Cardinals played were looked at based on the actual time in Phoenix on the date of the game) is playing in primetime against a team from two or more time zones to the east, the more western team wins 55.42% of the time (Author’s note: These numbers are current through Week 15 of the 2018 NFL season). That makes being the more western team in a primetime game almost as big of an advantage as being the home team in a random NFL game.

So, if this body clock matter actually has an effect on on field performance, we’d expect the effects to show up and alter the home field advantage of teams. To look at this, I broke the sample of 332 games played in primetime down to two groups:

  • The team that plays in the Eastern or Central Time zone is at home (Group 1) and
  • The team that plays in the Mountain or Pacific Time zone is at home (Group 2).

If the body clock issue actually exists for primetime games, we’d expect it to show up by dropping the primetime home winning percentage of Group 1 below .5781, while helping to prop the home winning percentage of Group 2 above .5781. Is this what we actually see?

Home team record in primetime by time zone when there is at least a two time zone difference

Group Home Winning Percentage Difference from NFL Overall Winning Percentage
Group Home Winning Percentage Difference from NFL Overall Winning Percentage
NFL Overall 0.5781 N/A
Group 1 (Eastern and Central Time Zone Teams at home) 0.5298 -0.0483
Group 2 (Pacific and Mountain Time Zone Teams at home) 0.6243 0.0462

What we see is a performance dip for Group 1 that is very, very close in size to the performance improvement we see for Group 2. Certainly interesting, but far from definitive, so let’s look at a little bit more data.

Specifically, if this body clock issue does indeed exist for primetime games, then we’d expect it to get larger as the time zone gap increases. Thus, since we already have the data set of all primetime games played between teams that are at least two time zones apart, what happens when we narrow it down even further to only look at primetime games that involve two teams that are three time zones apart?

That sample gets even smaller, as there have been only 152 games since 1976 which meet these criteria, but let’s see what the data looks like. Keeping things as similar to before as possible, let’s define two more groups.

  • The team that plays in the Eastern Time Zone is at home (Group 3) and
  • The team that plays in the Pacific Time Zone is at home (Group 4).

As noted, if this body clock effect is indeed real, we’d expect the impact on this sample to be even larger than on the prior group. So, without beating around the bush, let’s jump right to the data, which is as follows.

Winning percentage of home team when there is a three time zone difference between teams

Group Home Winning Percentage Difference from NFL Overall Winning Percentage
Group Home Winning Percentage Difference from NFL Overall Winning Percentage
NFL Overall 0.5781 N/A
Group 3 (Eastern Time Zone Teams at home) 0.3906 -0.1875
Group 4 (Pacific Time Zone Teams at home) 0.6552 0.0771

Before anybody asks, I won’t bother to bore everyone with the math behind the calculations, but the difference for Group 3 is statistically significant at the p < .01 level, while the other three groups are only statistically significant at the p < .25 level.

So, at some level, there is a measurable effect at play here. However, that does not necessarily mean that this is an effect which is in fact affecting NFL games. The sampling I have done here controlled only for time zones and home field. There was no account made for the actual quality of the teams playing, which could have a material impact on the results.

As such, while the results of the sampling I have done definitely seem to indicate that teams from further west have an advantage when playing teams from further east when the game takes place in primetime, it could simply be the result of quality teams, like the Seahawks, playing horrible teams, like the Green Bay Packers, in primetime over and over and over.

Thus, while this is something that I definitely find interesting, it will require some more digging before the results are truly reliable.